G.DENİZ DOĞAN-KÜLAHCI, ABİDİN TEMEL, Alain GOURGAUD, HÜNKAR DEMİRBAĞ

Afyon Volkanik Kayaçlarının (Batı Anadolu, Türkiye) Mineralojik- Petrografik Özellikleri ve P-T Hesaplamaları

Bu çalışmada Afyon ili güneyi ile Şuhut bölgesinin kuzeyi arasında bulunan volkaniklerin, mineralojik-petrografik özellikleri belirlenmiş ve mineral kimyası analizlerinden elde edilen veriler ile termobarometre hesaplamaları yapılmıştır. Çalışma alanında dom, lav domları ile blok ve kül akışları şeklinde görülen trakitik kayaçlarda gerçekleştirilen optik incelemeler sonucunda iki farklı mineralojik bileşim belirlenmiştir. Yüksek K2O, K2O/Na2O oranı ve Mg# değerlerine sahip olan kayaçlar ultrapotasik grup (UPG) olarak adlandırılmış ve ilgili grafiklere yerleştirildiğinde bu gruba ait örneklerin lamproyit tipi kayaç özelliği taşıdığı saptanmıştır. UPG kayaçlarının mineralojik bileşimi amfibol + flogopit + klinopiroksen + olivin + sanidin ve oksit mineraller olarak belirlenirken, diğer Afyon volkanik kayaçlarının mineralojik bileşimi plajiyoklaz + biyotit + amfibol + klinopiroksen ± ortopiroksen ± sanidin ve oksit minerallerden oluşmaktadır. Örneklerin çoğunluğunda hipokristalin porfirik doku gözlenirken, UPG örneklerinde holokristalin porfirik doku gözlenmektedir. Örnekler ana element kimyasal verilerine göre ortaç, karakterde (%52< SiO2< %63), trakit ve trakiandezit olup, tamamı alkali karakterdedir. Mikroprop analizlerinin değerlendirilmesi sonucunda, plajiyoklaz minerallerinin labrador-oligoklaz , amfibol minerallerinin çermakit, rihterit ve magnezyumlu-hornblend , klinopiroksen minerallerinin diyopsit, ojit ve ortopiroksenlerin hipersten kompozisyonunda olduğu belirlenmiştir. Optik mikroskop incelemelerinde sünger dokulu plajiyoklaz mineralleri gözlemlenmiş ve mikroprop, SEM (taramalı elektron mikroskobu) ve EDS (enerji dağılım spektrometresi) analizleri ile plajiyoklaz minerallerinin bazılarında ters zonlanma saptanmıştır. Bu veriler, Afyon volkanik kayaçlarının magma karışım sürecinden etkilenmiş olabileceğini işaret etmektedir. Bununla birlikte, klinopiroksen-eriyik ikilisinin dengede olduğu koşullar dikkate alınarak yapılan termobarometre hesaplamaları sonucunda, bu minerallerin oluşum sıcaklıklarının en düşük 1087 °C (AD5) ve en yüksek 1141 °C (AD3) olduğu belirlenmiştir. Basınç değerleri 5 ve 10 kbar aralığında değişirken, bu basınç değerleri kullanılarak elde edilen mineral kristallenme derinliklerinin ise, 18 km (AD5)-28 km (AD1) arasında olduğu belirlenmiştir. Klinopiroksen minerallerinin kristallenme derinliğinin farklı olması, bu minerallerin farklı derinliklerde oluşan farklı magma odalarında kristallenmiş olabileceğini düşündürmektedir.

Mineralogical-Petrographical Features and P-T Calculations of Afyon Volcanic Rocks (Western Anatolia, Turkey)

In this study, the mineralogical-petrographical properties of volcanics between the south of Afyon and the north of Şuhut are determined and by the help of the microprope analyses estimated thermobarometers are calculated. By the help of the previous studies, it is believed that the samples used in this study belong to early-stage volcanism products. As a result of the optical studies, two different mineralogical assemblages are determined from trachytic rocks, which are seen as domes, lava domes and block and ash flow in the study area. The volcanic rocks, which have high K2O, K2O/Na2O ratio and Mg# values, are classifed as ultrapotassic group (UPG) and when this group samples plotted related graphs it has been determined that they are lamproite-type rocks. The mineralogical assemblage of UPG rocks is amphibole + phlogopite+ clinopyroxene+ olivine+ sanidine and oxide minerals, the other Afyon volcanic rocks mineralogical assemblage is plagioclase + biotite + amphibole + clinopyoxene ± orthopyroxene ± sanidin ± phlogopite and oxide minerals. The majority of the samples displaying hypocrystalline porphyritic texture whereas UPG samples have holocrystalline texture. According to major element geochemical data, samples are intermediate trachyte and trachyandesites in composition (52%< SiO2< 63%) and all are alkaline in features. Microprobe analyses reveal that plagioclases are identified as labradorite-oligoclase , amphibole minerals are tschermakite, richterite, magnesiohornblend , clinopyroxenes are diopside, augite and orthopyroxenes are hypersthene in composition. The optical microscopic studies reveals that some plagioclases are reversly zoned and the spongy texture plagioclases are determined at microprobe, SEM (scanning electron microprobe) and EDS (energy-dispersive spectroscopy) analyses. All these suggest that Afyon volcanics can be affected by magma mixing process. However, the calculated minimum temperature is 1087 oC (AD5) and the maximum is 1141 oC (AD3), respectively as a result of thermobarometer calculations which took place in clinopyroxene-liquid equilibria conditions. The pressure values vary from 5-10 kbar, by using the pressure values the calculated mineral crystallization depths are between 18 km (AD5) - 28 km (AD1). The different crystallization depth of clinopyroxenes suggests that these minerals may be crystallized different magma chambers located at different depths.

PDF

___

Akal, C. 2003. Mineralogy and geochemistry of melilite leucites, Balıkçıhisar, Afyon; Turkey. Turkish Journal of Erath Science, 12, 215-239.
Akal, C. 2008. K-richterite-olivine-phlogopitediopside-sanidine lamproites from the Afyon volcanic province, Turkey. Geological Magazine, 145, 570-585.
Akal, C., Helvacı, C., Prelevic, D., ve Van den Bogaard, P. 2013. High-K volcanism in the Afyon region, western Turkey: from Si-oversaturated to Si-undersaturated volcanism. International Journal Science, 102, 435-453.
Aydar, E., Bayhan, H., ve Gourgaud, A. 2003. The lamprophyres of Afyon stratovolcano, western Anatolia, Turkey: description and genesis. Comptes Rendus Geoscience, 335, 279-288.
Besang, C., Eckhart, F.J., Harre, W., Kreuzer, H., ve Muller, P. 1977. Radiometriche Altersbestimmungen an neogenen Eruptigesteinen der Türkei. Geologisches Jahrbuch, 25, 3-36.
Best, M.G., 1982. Igneous and Metamorphic Petrology, Freeman, Appendix E, 616-619.
Biryol,C.B., Beck, S.L., Zandt, G., ve Özacar, A.A. 2011. Segmented African lithosphere beneath the Anatolian region inferred from teleseismic P-wave tomography. Geophysical Journal International, 184, 1037-1057.
Çemen, I., Catlos, E.J., Göğüş, O., ve Özerdem, C. 2006. Post-collisional extensional tectonics and exhumation of the Menderes Massif in the Western Anatolia Extended Terrane, Turkey. In: Dilek, Y (ed) Postcollisional tectonics and magmatism in the Eastern Mediteranean Region: GSA's Special Publication, 409, 353-379.
Çoban, H. 2007. Basalt magma genesis and fractionation in collision and extension-related provinces: A comparasion between eastern, central and western Anatolia. Earth-Science Reviews, 80, 3-4, 219-238.
Çoban, H., ve Flower, M.F.J. 2007. Late Pliocene lamproites from Bucak, Isparta (southwestern Turkey): Implications for mantle " wedge" evolution during Africa-Anatolian plate convergence. Journal of Asian Earth Sciences, 29, 1, 160- 176.
Faccenna, C., Piromallo, C., Crespo-Blanc, A., Jolivet, L., ve Rossetti, F. 2004. Lateral slab deformation and the origin of the western Mediterranean arcs. Tectonics, 23, TC1012.
Foley, S.F., Venturelli, G., Green, D.H. ve Toscani, L. 1987. The ultrapotassic rocks: characteristics, classification and contraints for petrogenetic models. Earth Science Reviews, 24, 81-134.
Glondy, J., ve Hetzel, R. 2007. Precise U-Pb ages of syn-extensional Miocene intrusions in the central Menderes Massif, western Turkey. Geological Magazine, 144, 235-246.
Işık, V., Tekeli, O., ve Seyitoğlu, G. 2004. The 40Ar/39Ar age of extensional ductile deformation and granitoid intrusion in the northern Menderes core complex: implications for the initiation of exsional tectonics in western Turkey. Journal of Asian Earth Science, 23, 555-566.
Kibici, Y., Dinç, D., ve Uçar, A. 2012. Afyonkarahisar yöresi volkanik kayaçlarının mineralojik ve petrografik özellikleri. Dumlupınar Üniversitesi, Fen Bilimleri Enstitü- sü Dergisi, 29, 53-70.
Leake, B.E., Woolley, A.R., Arps, C.E.S., Birch, W.D., Gibert,M.C., Grice, J.D., Hawthorne, F.C., Kato, A., Kisch, H.J.,Krivovichev, V.G., Linthout, K., Laird, J., Mandarino, J.,Maresch, W.V.,
Nickel, E.H., Rock, N.M.S., Schumacher, J.C., Stephenson, N.C.N., Whittaker, E.J.W. ve Youzhi, G. 1997. Nomenclature of amphiboles: report of the Subcommitteeon Amphiboles of the International Mineralogical Association Commission on New Minerals and Mineral Names. Mineralogical Magazine, 61, 295-321.
Le Bas, M.J., Le Maitre, R.W., Streckeisen, A. ve Zanettin, B. 1986. A Chemical Classification of Volcanic Rocks Based on the Total Alkali - Silica Diagram. Journal of Petrology, 27, 745-750.
Masotta, M., Mollo, S., Freda, C., Gaeta, ve Moore, G. 2013. Clinopyroxene-liquid thermometers and barometers specific to alkaline differentiated magmas. Contributions to Mineralogy and Petrology, 166, 1545-1561.
Miyashiro, A. 1978. Nature of alkalic rock series, Contributions to Mineralogy and Petrology, 66, 91- 104.
Morimoto, N. 1989. Nomenclature of pyroxenes. Canadian Mineralogist, 27, 143-156.
Nimis, P. 1995. A clinopyroxene geobarometer for basaltic systems based on crystalsstructure modeling. Contributions to Mineralogy and Petrology, 121, 115- 125.
Nimis, P., ve Ulmer, P.1998. Clinopyroxene geobarometry of magmatic rocks, Part 1:
an expanded structural geobarometer for anhydrous and hydrous basic and ultrabasic systems. Contributions to Mineralogy and Petrology, 133, 122-135.
Nimis, P., ve Taylor, W.R. 2000. Single clinopyroxene thermobarometry for garnet peridotites, Part 1: Calibration and testing of a Cr-İn cpx barometer and an enstatite-in-cpx thermometer, Contributions to Mineralogy and Petrology, 139, 541-554.
Prelevic, D., Akal, C., Foley, S.F., Romer, R.L., Stracke, A., ve Van Den Bogaard, P. 2012. Ultrapotassic mafic rocks as geochemical proxies for postcollisional mantle dynamics of lithosphere: the case of SW Anatolia-Turkey. Journal of Petrology, 53, 1019-1055.
Prelevic, D., Akal, C., Romer, R.L., Mertz-Kraus, R., ve Helvacı, C. 2015. Magmatic Response to Slab Tearing: Constraints from the Afyon Alkaline Volcanic Complex, Western Turkey. Journal of Petrology, 1-36. Putirka, K., Johnson, M., Kinzler, R., ve Walker, D. 1996. Thermobarometry of mafic igneous rocks based on clinopyroxene-liquid equilibria, 0-30 kbar, Contributions to Mineralogy and Petrology, 123, 92- 108.
Putirka, K., Mikaelian, H., Ryerson, F., ve Shaw, H. 2003. New clinopyroxene-liquid thermometers for mafic, evolved, and volatile-bearing lava compositions, with applications to lavas from Tibet and the Snake River Plain, Idaho, American Mineralogist, 88, 1542-1554.
Putirka, K. 2008. Thermometers and Barometers for Volcanic Systems, Minerals, Inclusions and Volcanic Processes, Reviews in Mineralogy and Geochemistry, (eds: Putirka, K., Tepley, F.), Mineralogical Society of America, 69, 61-120.
Rimmelé, G., Oberhansli, R., Goffé, B., Jolivet, L., Candan, O., ve Çetinkaplan, M. 2003. First evidence of high- pressure metamorphism in the ' Cover Series' of the southern Menderes Massif. Tectonic and metamorphic implications for the evolution of SW Turkey. Lithos, 71, 19-46.
Ring, U., ve Collins, A.S. 2005. U-Pb SIMS dating of synkinematic granites: timing of core-complex formation in the northern Anatolide belt of western Turkey. Journal of the Geological Society, London, 162, 289-298.
Savaşçın, M.Y., ve Güleç, N. 1990. Relationship between magmatic and tectonic activities in W. Turkey. IESCA Proceedings II, 300-331.
Seyitoğlu, G., ve Scott, B.C. 1996. The cause of N-S extensional tectonics in western Turkey: tectonic escape vs back-arc spreading vs orogenic collapse. Journal of Geodynamics, 22, 145-153.
Sparkman, W., ve Wortel, M.J.R. 1988. The Hellenic subduction zone: a tomographic image and its geodynamic implications. Geophys Res Lett, 15, 60-63.
Şengör, A.M.C., Satır, M., ve Akkök, R. 1984. Timing of tectonics events in the Menderes Massif, western Turkey: implications for tectonic evolution and evidence for Pan-African basement in Turkey. Tectonics, 3, 693-707.
Şengör, A.M.C. 1985. Strike-slip faulting and related basin formation in zones of tectonic escape: Turkey as a case study. In: Biddle KT, Christie-Blick N(eds). Strikeslip deformation, and formation, and sedimantation. SEPM Special Publication, 37, 227-264.
Van Hinsbergen, D.J.J., Kaymakçı, N., Sparkman, W., Torsvik, ve T.H.2010. Reconciling the geological history of western Turkey with plate circuits and mantle tomography. Earth Planet Science Letters, 297, 674-686.
Westeway, R. 2006. Cenozoic cooling histories in the Mebnderes Massif, western Turkey, may be caused by erosion and flat subduction, not low-angle normal faulting. Tectonophysics, 412, 1-25.
Wortel, M.J.R., ve Sparkman, W. 2000. Subduction and slab detachment in the Mediterranean-Carpathian region. Science, 290, 1920-1917.
Yılmaz, Y., Genç, C., Gurer, F., Bozcu, M., Ylmaz, K., Karacık, Z., Altunkaynak, S., ve Elmas, A. 2000. When did the wes tern Anatolian grabens begin to develop? In: Bozkurt, E., Winchester, J. A.
and Piper, J. D.A. (eds). Tectonics and Magmatism in Turkey and the Surrounding Area. Geological Society, London, Special Publications, 173, 353-384.